Pathological lying is a behavior of habitual or compulsive lying.
What is Compulsive or Pathological Lying? // Kati Morton by Kati Morton
It was first described in the medical literature in 1891 by Anton Delbrueck.
The truth about "pathological liars" by gerlach
Although it is a controversial topic, pathological lying has been defined as "falsification entirely disproportionate to any discernible end in view, may be extensive and very complicated, and may manifest over a period of years or even a lifetime".
Sometimes however, the individual may be lying to make their life seem more exciting when in reality they believe their life is unpleasant or boring.